About 6 months ago mt sr1803wm was doing the exact same things. I'd have to pull the power plug to rest it and wait then plug back in and restart until it terminally refused to start.
I followed seral hints on yanking the cmos battery with it unplugged and a very nise one on both a smos and bios reset using the jumpers on my board.
Since then I've replaced the cpu,mobo and power supply.
1 fan kicks on and the drives power,this is due to they get power off the supply but the board is still DOA. No beep as it powers as it never even gets to a POST - power on self test. No signal goes to the video and the keyboard check lights never go on as if during a post, I'm beside myself and nearly $100 bucks into parts that for all intents are a whole new pc. Just a whole new dead one. Go figure.
If you find out, tell me would ya?
2 days ago i tried to turn on the PC and it wouldn't completely boot up. It stayed locked in that high pitched mode and i had to hold the power button in to shut it down. This happened twice that morning. The second time after it was shut down i pulled out the power cord from the back(for added measure). An hour later i tried to turn it on and it was completely dead although the small power indicator light is on albeit weak and blinking. I have been doing some reading on similar topics here on Cnet(and other sites) and am wondering if it is the PSU. I have tested my power cord , i checked the internal power on/off switch to make sure it wasn't the problem and have tried different outlets. The PC is dead for whatever reason. How would i know if it is in fact the PSU or something else like the mother board? Is there an internal fuse that i should look at? I opened up the body and cleaned it out(it was filthy of course) but being ignorant to the high tech world of PCs I don't want to be too invasive without asking for advice here..keep in mind that my Compaq Presario is 6 years old but has been updated ,typical problems ,previously reformatted etc etc. Thanks to all in advance for any help